Process for the manufacture of mixed base sodium calcium greases



Patented Dec. 1, 1959 Refining Company, New York, N.Y., a corporation of Maine N Drawing. Application April 1, 1955 Serial No. 498,784

2 Claims. (Cl. 252-40) This invention relates to mixed base sodium-calcium greases. In particular, the present invention is concerned with a method of manufacturing mixed base sodiumcalcium greases whereby certain desirable grease fibre structure is obtained.

In the copending application of Francis E. Chamberlin, Serial No. 481,010, filed January 10, 1955, is disclosed the discovery that the fibre structure ofmixed base sodium-calcium 12-hydroxy stearate greases determines the performance of such greases and the properties of such greases can he predicted with surprising accuracy from a knowledge of the physical nature of the elemental structure of the grease. As disclosed in the application of Chamberlin, a desirable fibre structure of mixed base sodium-calcium greases can be obtained by careful con trol of dehydration during the nucleation of the grease fibres of the final composition. More specifically, it was descovered that nucleation of the final fibres occurs during removal of about the final 2.5 to2.0 percent of the water, based on the soap content, and that this water must be removed at a very high rate to insure the desired fibre structure of the final grease. Under certain processing conditions, it may be difiicult to obtain the necessary high rate of dehydration without the use of special handling techniques.

I have now discovered an especially advantageous method of efiecting dehydration of mixed base sodiumcalcium 12-hydroxy stearate greases whereby proper fibre structure of the resulting grease is insured. I have also discovered a method whereby mixed base sodiumcalcium l2-hydroxy stearate greases having undesirable fibre structure or having unknown fibre structure can be treated in a manner which results in a greasewith the desired fibre structure.- These advantages are effected in accordance with my invention in a manner substantially independent of operator technique and skill.

The aforementioned Chamberlin application discloses the discovery that mixed base sodium-calcium 12-hydroxy stearate greases require a fibre structure characterized by heterogeneous thin and narrow ribbon-like fibres with the larger fibres bent and twisted to have the properties necessary to provide satisfactory service under the conditions encountered during use of these greases. This fibre structure results upon rapid dehydration during the final nucleation of fibres of such greases while maintaining substantially constant pressure on the grease. With this in mind, the essence of the present invention can be described as a controlled reconstitution or renucleation of the fibres of a mixed-base sodium-calcium 12-hydroxy stearate grease to insure a final fibre structure of the character described.

Reconstitution of fibre structure is accomplished in accordance with my invention by adding water to destroy the fibres present in a dehydrated but unfinished mixed base sodium-calcium grease and then again dehydrating the unfinished grease employing a rapid dehydration rate found to be necessary as described by Chamberlin. This is effected by adding Water to a hot dehydrated grease soap base or grease at an elevated temperature. By the terms grease soap base and grease base, I intend mixtures of soaps and starting oil as exist at the point in grease making procedures when finishing oil normally would be added to the dehydrated mass. The quantity of water employed is sufiicie'nt to eifect solution of, or otherwise destroy, the soap fibres in the mass at the temperature involved. Generally, the quantity of water necessary to effect solution of the fibres is equal to the amount present at the instant final nucleation would begin which, as disclosed by Chamberlin, is about 2.5 to 2.0 weight percent, based on the soap. Therefore, to effect my invention I add at least 2.5 percent water and preferably 3 or more percent, based on the soap content. A particularly desirable amount of water to be added ranges from about 3 weight percent to 10 weightpercent based on the soap present in the mass being treated.

As discussed above, the present invention is efiected by adding the defined quantity of water to a hot dehydrated grease which is maintained at substantially constant pressure and which is at a temperature sufiiciently high that dehydration will be efiected rapidly, or is maintained at a sufiiciently high temperature by the addition of heat, as by indirect heating with steam, that the water will be removed at the necessary high rate. It has been determined that as long as the grease is at a temperature above 300 F. during removal of the Water present during nucleation of the final fibres, the rate of dehydration is sufiicient to result in a fibre structure characterized by heterogeneous thin and narrow ribbon-like fibres with the larger fibres bent and intertwined for grease batches of about 400 to about 15,000 pounds. The upper temperature limit employed generally is determined by the amount of grease being handled and the temperature stability of the soap fibres. Larger quantities of grease require higher temperatures, i.e., about 325 to 350 P. On the other hand, a temperature of 340 F. maintained for a long period of time will result in melting the fibres so it is incumbent upon the operator, when using temperatures of 335 F. and higher, to cool the grease (stop heating) substantially immediately upon completion of the dehydration. While it has been stated in this specification that certain amounts of water are removed, it

should be understood that an absolute anhydrous state is not essential. Thus, as a practical matter, the Water content is reduced to at least below 1.0 percent and pref- I erably below about 0.5 percent, for example, about 0.1 percent.

Mixed base sodium-calcium IZ-hydroxy stearate greases which can be treated in accordance with the present invention contain sodium and calcium 7 in a weight ratio of about 3 to 10 parts of sodium per part of calcium. These can be employed in any of the usual forms, for example, as oxides, hydroxides, hydrated oxides, carbonates, etc. In the preferred greases a 4 to 6:1 and particularly 5:1 ratio of flake caustic to hydrated lime is employed.

The fatty components employed can be substantially pure l2-hydroxy stearic acid or its glycerides, e.g., hydrogenated castor oil. Particularly satisfactory greases employ hydrogenated castor oil saponified by the sodium component and 12-hydroxy stearic acid saponified by the calcium. In such greases the fatty components are preferably employed in a weight ratio of hydrogenated castor oil to 12-hydroxy stearic acid of about 3 to 10:1 and preferably 4 to 6:1, particularly 5:1. The total soap content of the final grease compositions is normally about 10 to 25 weight percent and preferably 15 to 20 weight percent.

The oil component of greases employed in my invention can be synthetic or mineral base and the oil can be highly refined and solvent treated if desired. Preferably 3 amineral base lubricating oil is employed. Suitably the oil has a viscosity of about '50 to 1500 SUS at 100 F. with about 100 to 150 SUS being the preferred range. Normally the final grease compositions analyze at about 75 to 90 weight percent oil with about 80 to 85 percent being average.

The instant invention can be practiced on mixed base sodium-calcium 12-hydroxy stearate greases howeverprepared and however dehydrated. Thus, a grease can be manufactured without regard to the fibre structure, dehydrated in any manner desired and the resulting dehydrated grease then can be treated in accordance with my process. By so treating the grease, the final fibre structure will be determined by the rate that dehydration of the added water is eifected and will be completely independent of any processing variables which were employed prior to the addition of the defined quantity of water. Various procedures which can be employed to obtain mixed base sodium-calcium greases or grease soap bases include blending sodium and calcium greases together in the desired proportions, making the soap bases separately and then combining and finishing the grease by adding the soap bases as a mixture, and by employing low or high temperature conditions for mixing, saponification and the like. A highly desirable procedure is the reverse saponification technique which involves saponifying hydrogenated castor oil in starting oil with the sodium component and then adding l2-hydroxy stearic acid to the mass and saponifying the acid with the calcium component. Reverse saponifica-tion also is disclosed in the cited Chamberlin application.

The process constituing my invention is most advan-. tageously practiced on grease soap bases ratherthan finished greases because less material need be handled. Thus, after dehydration of the mixture of starting oil and soaps and while the mass is still hot, water is added in accordance with the instant process and reconstitution of the fibres is effected whereupon finishing oil is added in the usual manner. Obviously greases already containing finishing oil also can be treated. -It also should be understood that the usual additives, such as antioxidants; extreme pressure additives and the like can be present in the normal amounts so long as they do not deleteriously alfect the invention.

The inventionwill be described further in conjunction with the following specific examples. A blend of solvent treated Mid-Continent neutral oils is employed in Example l. The blend has the following characteristics:

AP I gravity 32.5 Flash point .F 395 Fire point F 455 Viscosity at 100 F. SUS 126 Viscosity at 210 F. SUS 41.43 Viscosity index 96 Pour point F Example I One part of oil blend and one part of hydrogenated castor oil are charged to a grease kettle. Heat is applied to the kettle and the temperature of the mixture isbrought to about 200 F. and held until all the castor oil has melted, whereupon a stoichiometric quantity of caustic soda is added. The caustic is added as a 50 percent solution in Water. After the resulting foamingsubsides, dry, solid IZ-hydroxy stearic acidis added. and upon melting, alimc-oil slurryin the ratio of 1 part liine to 7'parts of oil is added. The temperature is permittedrtorise, whereupon saponification iscompleted and the free wateriwh'ich separates during sapon'ification-is evaporated. Thewtemperature is-further raised to permit substantially complete dehydration of the resulting mixture. Kettle temperature at this point is about 330? F. Whenthe grease-is completely, dehydrated, a quantity of water equivalent to about 3 percent of the soap present istadded while stirringthe previously dehydrated grease.

The added water effects Example. II

To demonstrate the feasibility of the present invention in producing fibre structures by renucleation whereby the properties of the resulting grease would be suitable for the purposes of Navy specification MIL-1,7711, a mixed base sodium calcium grease soap base, having a 50 percent-soap content was dehydrated in the usual manner, that is, by the slow procedure characteristic of grease dehydration before the Chamberlin discovery. At this point the water content was about 0.59 percent. An electron micrograph of this material disclosed that a considerableportion of the soap had not even formed into well-shaped. fibres or defined fibres and the large fibres present were.

straight and board-like.

A portion of the above grease was removed for reconstitution by the subject process while the remainder was finished in the usual manner by adding finishing oil until.

the desired penetration was obtained. The finished grease had essentially the same fibre structure as above.

described.

The portion of the above grease base which was removed before finishing Was heated to 340 F. in a kettle and then 5 percent of water was added while the temperature was maintained at 340 F. by the use of high pressure steam in indirect heat exchange relationship with the grease base for periods up to minutes. Electron micrograph study of samples of the grease base.

taken during various periods disclosed that the soap fibres were destroyed within about six minutes and, then a gradual reformation of the fibres took place. New fibres began to form within twenty minutes and at the end of 140 minutes substantially complete dehydration had been effected and the final fibre structure obtained. The final fibre structure consisted mainly of the long interlaced fibres recognized as essential tohave a satisfactory MIL-L 7711 grease and there was no-evidence of the undesirable small fibre and amorphous material present as was characteristic of the unsatisfactory grease. The grease was then finished in the usual manner.

Characteristics of greases as above prepared, that is, by reconstitution according to the instant invention and by dehydration in the usual manner of grease making, appear in the following table.

Typical Grease Re- Grease constituted Slow De- As In hydration Example 11 Soap Contentl3inished Grease, Percent 20.0 16.0 ASTM Worked Penetration 324 324 Worked 100,000 Strokes (Navy Worker) 354 859 geneous thin and narrow ribbon-like fibres with the largerfibres bent and intertwined. The method is especially advantageous because excellent greases .are obtained in a manner substantially independent of operator skill and technique.

I claim:

1. In the manufacture of substantially anhydrous mixed base sodium calcium grease characterized by heterogeneous thin, narrow, ribbon-like fibres and larger bent, twisted fibres wherein a lubricating oil is thickened to a grease consistency with mixed sodium and calcium 12- hydroxy stearates and the resulting oil-l2-hydroxy stearate mixture is dehydrated at an elevated temperature, the steps of adding water to the hot dehydrated oil-l2-hydroxy stearate mixture in an amount sulficient to eifect solution of fibres present and maintaining the mass at a temperature of about at least 300 F. and below the melting point of the fibres until the mass is again dehydrated while maintaining substantially constant pressure.

2. The method of claim 1 wherein about 3 to 10 weight percent of water, based on the soap present, is added.

References Cited in the file of this patent UNITED STATES PATENTS New York, N.Y., pp. 585-588 and 3843. 

1. IN THE MANUFACTURE OF SUBSTANTIALLY ANHYDROUS MIXED BASE SODIUM CALCIUM GREASE CHARACTERIZED BY HETEROGENEOUS THIN, NARROW, RIBBON-LIKE FIBRES AND LARGER BENT, TWISTED FIBRES WHEREIN A LUBRICATING OIL IS THICKENED TO A GREASE CONSISTENCY WITH MIXED SODIUM AND CALCIUM 12HYDROXY STEARATES AND THE RESULTING OLI-12-HYDROXY STEARATE MIXTURE IS DEHYDRATED AT AN ELEVATED TEMPERATURE, THE STEPS OF ADDING WATER TO THE HOT DEHYDRATED OIL-12-HYDROXY STEARATE MIXTURE IN AN AMOUNT SUFFICIENT TO EFFECT SOLUTION OF FIBRES PRESENT AND MAINTAINING THE MASS AT A TEMPERATURE OF ABOUT AT LEAST 300*F. AND BELOW THE MELTING POINT OF THE FIBRES UNTIL THE MASS IS AGAIN DEHYDRATED WHILE MAINTAINING SUBSTANTIALLY CONSTANT PRESSURE. 